Development And Validation Of A Wireless Method To Determine Arterial Pressure At Wrist Using Singular Value Decomposition

The main purpose of the thesis is to develop and realize a wrist blood pressure measurement system based on Singular Value Decomposition (SVD), depended on the research of blood pressure measurement at wrist and the application of short range radio communication. Several new techniques have been studied in this dissertation.Firstly, a new algorithm of wrist oscillometric blood pressure-measuring using singular value decomposition was presented. This algorithm could be subdivided into SVD and curve fitting algorithm (SCFA). In order to obtain oscillation waveforms, we used a digital band filter to remove the interference of low-frequency and high-frequency components. Then we used the Singular Value Ratio (SVR) spectrum, developed on the basis of the SVD, to detect the periodic component. SVR spectrum can provide an estimation of the period length of the most dominant periodic component present in any signal. We obtain a spectrogram matrix according to the periodic length. Final we used SVD to extract the dominant component of oscillation waveforms. Then oscillation amplitudes of dominant component and cuff pressure were used to determine arterial blood pressure (ABP) with curve fitting algorithm. Our algorithm could eliminate the intrinsic noise due to ulnar arterial vibration of the wrist and thus increase the measurement accuracy. Evaluated with the simulated signals constructed from the standard oscillation waves corrupted by the noise of the same frequency spectrum, the algorithm showed its excellent performance in noise rejection. To test the performance of this algorithm, 45 subjects underwent the ABP measurement using both the auscultation and the oscillometry combined with the SCFA. Results demonstrated that the proposed SCFA was superior in accuracy and robustness to the traditional curve fitting algorithm (TCFA).Secondly, a new platform for gathering the data about blood pressure at wrist was provided. Developed from the oscillometric measurement circuit, the circuit of platform can perform not only the oscillometric measurement but also continuously pulse measurement with low cuff pressure. Our platform was suitable for portable application in dimension and power consumption.Thirdly, the design and implementation of wireless interfaces were put forward, relied on Short Range Radio Communication Technologies. Wireless interfaces were used to complete the wireless wrist measurement platform. According to the potential requirements of platform application, three kinds of short range radio communication technologies were selected to construct wireless interfaces. Firstly, wireless interface was designed and completed on the basis of non-standard wireless communication chip nRF24L01, and its power consumption was lower in test, compared with other wireless technology. Secondly, because of information exchanging ability of Bluetooth technology, Bluetooth chip BlueCore4-External was used to implement designed wireless interface. Test results revealed that it could be set up between fixed and mobile devices with low cost. Thirdly, wireless interface on zigbee technology, a kind of wireless mesh networking, was establish on IP-LINK zigbee modules, for indoor propagation. The experiment results showed the mix of"static"and"mobile"nodes provided full coverage in 20 rooms, and the packet delays by router were met for measurement applications.Fourthly, a new wrist blood pressure measurement system was given birth. The system could be subdivided into gathering segment and processing segment under"client/server"framework. The signals about blood pressure were collected by portable gathering segment, acted as client, and transmitted by wireless interfaces from client to server, processed by processing segment acted as server. The system could perform more excellent on signal processing by the use of this framework.According to the new algorithm of wrist oscillometric blood pressure-measuring based on SVD, software was assembled to complete the oscillometric measurement on server of the new wrist blood pressure measurement system.Fifthly, a new approach for wireless continuous blood pressure measurement was brought forth. Our approach employed the wrist gathering platform to acquire the continuous pulse vibration at the artery of wrist undertaken low cuff pressure approach, then used server to accept the pulse signals through wireless interfaces, analysed the blood pressure according to translating formula of blood pressure and pulse vibration.What's more, according to relations between characteristic parameters of pulse waves and information about the cardiovascular system, wrist blood pressure measurement could be used to monitor the shape changes of pulse waves to evaluate the cardiovascular system and peripheral vascular resistance variety.At present, oscillometric blood pressure measurement and continuous blood pressure measurement could be carried out by wireless wrist blood pressure measurement system based on SVD, under the wrist cuff. This system could exploit a new effectual approach for self blood pressure measurement at home and blood pressure measurement at clinics because of low cost and easy operation.